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F. R. Forsyth, I. V. Hall, and H. J. Lightfoot

Abstract

Outward diffusion of CO2 from ‘Stevens’ and from native seedling cranberries (Vaccinium macrocarpon Ait.) collected in 1971 and held 6 months at 3°C proceeded at the rate of 4.55 and 2.56 μl/cm2-hr, respectively. The rate of movement of O2 into ‘Stevens’ was 2.64 and for a native seedling was 3.28 μl/cm2-hr. For cranberries collected in 1972 and held 1 month at 3°C the respective values for CO2 were 1.48 and 1.53 and for O2 they were 3.09 and 3.65 μl/cm2-hr.

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Nicole R. Gorman and Mark C. Starrett

Studies were conducted to examine the host range of a select isolate of the ericoid mycorrhizal fungus, Hymenoscyphus ericae (Read) Korf and Kernan [American Type Culture Collection (ATCC) #32985]. Host status was tested for 15 ericaceous species, including Calluna vulgaris, Enkianthus campanulatus, Gaultheria procumbens, Kalmia latifolia, Leucothoe fontanesiana, Oxydendrum arboreum, Pieris floribunda, Rhododendron calendulaceum, Rhododendron carolinianum, Rhododendron catawbiense, Rhododendron maximum, Rhododendron mucronulatum, Vaccinium corymbosum, and Vaccinium macrocarpon. Arbutus unedo, an ericaceous species that forms arbutoid, not ericoid, mycorrhizae was used as a negative control. All of the species were colonized by the ericoid isolate with the exception of Enkianthus campanulatus and the negative control. The benefits of the association and possible commercial applications are discussed.

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Carolyn DeMoranville

With dwindling funding for horticultural research, the need to conduct experiments which are the most efficient in terms of resource (including personnel) utilization becomes apparent. Research on minor crops such as cranberry (Vaccinium macrocarpon, Ait.) has been particularly hard-hit by the funding crunch. A study to generate a large database as the basis for future experimental design was initiated in 1986 for the variety `Early Black' (60% of MA commercial acreage). Seasonal nutrient levels for all tissues, patterns of biomass development, components of yield, and fruit development were included. In 1989, the study was expanded to include a comparison of 6 MA varieties grown under the same cultural and environmental condition. A portion of the database will be presented and its implementation to increase field experiment efficiency will be discussed.

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Hilary A. Sandler and Carolyn J. DeMoranville

Field conditions associated with commercial cranberry (Vaccinium macrocarpon Ait.) production were simulated in greenhouse studies to determine the effect of soil surface characteristics on dichlobenil activity. Sand was compared with organic matter, in the form of leaf litter, as the surface layer. A seedling bioassay using alfalfa (Medicago sativa L.), a dichlobenil-sensitive plant, was employed to determine root growth response on herbicide-treated soil. When the herbicide was applied to a sand surface, root growth was greater as time after application elapsed, indicating loss of herbicide activity. Conversely, the presence of organic matter on the surface prolonged the activity of the herbicide. Composition of the surface layer was more important than the depth of the layer in determining herbicide persistence. The influence of cultural practices, such as the application of sand or the removal of surface debris, on herbicide activity should be considered when planning weed management strategies for cranberry production. Chemical name used: 2,6-dichlorobenzonitrile (dichlobenil).

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Kris L. Wilder, Timothy L. Righetti, and Arthur Poole

Cranberry (Vaccinium macrocarpon Ait.) is an important crop in Oregon. However, nutrient critical levels have not been established. Since developing nutrient critical levels usually requires time-consuming and expensive field trials, we chose to use the Diagnosis and Recommendation Integrated System (DRIS), which can use survey data to determine critical levels. We analyzed 139 cranberry samples collected from the southern Oregon coastal area over a three-year period. Leaf concentrations for N, P, K, S, Ca, Mg, Mn, Fe, Cu, B, and Zn in bearing uprights collected in mid-August were matched with the corresponding yields. DRIS was employed to obtain norms and critical levels from this survey data. To test our DRIS norms and critical levels, we evaluated two published experiments (Torio and Eck, 1969 and Medappa and Dana, 1969) where fertility treatments altered mineral concentrations and affected yield. Both ratio-based and critical concentration diagnoses were useful. Changes in the Nutrient Imbalance Index was a good predictor of yield response.

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J. R. Davenport

Foliar feeding of crop plants is an increasingly popular practice. The use of foliar nutrients relies on the ability of the plant to sorb nutrients through the leaves. Cranberries (Vaccinium macrocarpon Ait.) are known to have a waxy cuticle on the leaf surface which may impede nutrient uptake, leaving only the lower leaf surface for effective uptake. This study was undertaken to determine the extent of foliar nutrient uptake by cranberries using rubidium as a tracer. Rubidium was chosen for its similarity to potassium in plant uptake. In replicated plots, cranberries were sprayed with rubidium at the rate recommended for foliar potassium at three different growth stages and three different times of day. Washed and unwashed leaves were analyzed one day, one week, and one month after rubidium applications. Stem, soil, and root material was analyzed for rubidium at the one week and one month sample times. Results will be discussed with reference to uptake and movement of foliar applied nutrients in cranberries.

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Elden J. Stang and John Klueh

Spunbonded polypropylene fabric covers were applied over mature `Searles' cranberry (Vaccinium macrocarpon Ait. in the field during dormancy in 1989. Covers were selectively removed at 3 week intervals in April, May and early June after onset of growth. Plant canopy air temperatures under fabric were 5 to 6C higher than in exposed controls. Temperature differences up to 17C were measured in early June. Soil temperatures did not differ from the control until late May. Earlier greening of leaf tissue resulted in increased photosynthetic rates earlier in the growing season under fabric covers. Subsequent shoot dry weight was increased 5%; leaf size was not affected. A trend to increased fruit set (4 to 6%) with fabric cover treatments was observed when covers were applied for 6 or 9 weeks. Total fruit yield and anthocyanin content were not appreciably influenced by fabric covers.

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Karim M. Farag, Jiwan P. Palta, and Elden J. Stang

The application of ethanol for enhancing effectiveness of ethephon under field conditions on cranberry (Vaccinium macrocarpon Ait.) fruit was tested during three seasons (1986 to 1988). The formulation containing ethephon plus the surfactant Tergitol (0.3% or 0.5%, v/v) and ethanol (2.5%, 5%, or 10%) consistently increased anthocyanin content in the fruit by 28% to 54% over the control. In general, fruit size was not affected by the ethephon treatment containing ethanol and Tergitol. The application of ethephon plus surfactant did not increase the anthocyanin content in the fruit. The presence of ethanol in the ethephon and surfactant mixture, however, consistently enhanced the fruit anthocyanin content by 21% to 40% as compared to ethephon plus surfactant. No adverse effect of various treatments on vine growth or appearance was noticed over the three seasons. Chemical name used: (2-chloroethyl) phosphonic acid (ethephon).

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Kim D. Patten and John Wang

The relationships between canopy density of three perennial weed species (Potentilla pacifica Howell, Aster subspicatus Nees, and Lotus corniculatus L.) and `Mcfarlin' and `Stevens' cranberry (Vaccinium macrocarpon Ait.) yield and fruit quality were evaluated. Yield was more severely affected by weed interferences than fruit size or color. Best-fit regression equations for the effects of weed density on yield, fruit size, and color were linear or quadratic polynomials with a strong linear component. For each bog, the slope of the linear relationship between yield and weed density was more negative as the mean yield of weed-free controls increased. `Stevens' fruit size and yield were more sensitive and fruit color was less sensitive to changes in P. pacifica population density than those of `McFarlin'.

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Bernadine C. Strik and Arthur Poole

Timing and severity of pruning in a 30-year-old commercial `McFarlin' cranberry (Vaccinium macrocarpon Ait.) bed were studied. Treatments in 1989 and 1990 consisted of early or late pruning and heavy, moderate, light, or no pruning. Yield component data were collected in Fall 1989 and 1990, just before harvest. Time of pruning did not affect yield components. In 1989, the unpruned and lightly pruned vines had a higher total plant fresh weight, fewer berries, higher berry yield, longer and more fruiting uprights, and fewer nonfruiting uprights (U,) compared with moderately or heavily pruned vines. Average length of UN and anthocyanin content of berries in 1989 were not influenced by pruning. In 1990, the effects of pruning severity were similar to 1989. In 1990, unpruned vines had a lower percent fruit set and berries contained less anthocyanin than pruned vines. Annual pruning with conventional systems in use decreases yield.